Permeation characteristics and cross-linking efficacy of iontophoresis-assisted riboflavin delivery for accelerated riboflavin-ultraviolet A scleral collagen cross-linking in porcine eyes

The purpose of this study is to investigate whether the iontophoresis-assisted riboflavin delivery to posterior sclera with less delivery time, can achieve the same riboflavin permeation efficiency as the passive soaking way, and its effect on the mechanical properties of posterior sclera for accelerated scleral collagen cross-linking (A-SXL). In this study, 0.1% riboflavin solution was applied into the posterior sclera of porcine eyes either by the iontophoresis-assisted or passive soaking method, with delivery time of 5, 7.5, 10, 12.5, 15, 17.5, and 20 min, respectively. The fluorescence intensity and the distribution of riboflavin concentration in the 10 μm frozen sections of the sclera were evaluated by fluorescence inverted microscope. The posterior sclera with riboflavin treatment through either the iontophoresis-assisted or the passive soaking method for different durations ranging from 5 to 20 min was treated with ultraviolet A (UVA) irradiation at an intensity of 10 mW/cm² for 9 min. The elastic modulus was determined at the physiological strain level using the uniaxial tensile test after ASXL. The results showed that the fluorescence intensity of riboflavin increased by prolonging the delivery time in both the iontophoresis and passive soaking groups, and the permeation depth of riboflavin remained constant over 15 min. The fluorescence intensity in the iontophoresis group was significantly higher than in the passive soaking group at 12.5 min and 15 min, respectively. The elastic modulus at 12.5 min in the iontophoresis group was significantly higher than in the passive soaking group at the same delivery time and showed no significant difference compared to the passive soaking group at 20 min. In conclusion, it indicated that iontophoresis-assisted delivery could not only shorten the surgery time but also achieve similar mechanical performance to the passive soaking method in ASXL.